The present invention relates to a motor-driven system for steering a vehicle, characterized in that the steering control device (e.g. steering-wheel) and the steering device (e.g. steering-box) are connected through a motorized device suitable to transmit to the steering device a movement having an amplitude different from the movement given to the steering control device by the pilot, said change of amplitude being variable according to various parameters.
When the vehicle is steered through the control device and the motorized device is operating, said motorized device can amplify the movement transmitted to the steering device with respect to the movement given to the steering control device by the pilot. In this case, the work of the pilot, which gives on said control device a reaction comparable with the action he would have given in the absence of the motorized device, is smaller than that which would have been otherwise required, and the steering is facilitated, in particular in small radius manouvres.
Moreover, the motorized device, when properly controlled, can even reduce the amplitude of the movement transmitted to the steering device with respect to the movement given to the steering control device by the pilot, thus reducing the effect on the steering device of the pilot's action.
The applicant, on the basis of his knowledge of the state of the art, believes that no devices have been on sale, or subject-matter of patent applications, which achieve the advantages of the subject-matter of the present invention.
A number of devices, even electrical ones, suitable to reduce the steering work, known as power steerings, are characterized in that the steering movement given by the pilot remains unchanged between the inlet and the outlet, while the force or torque which the pilot applies on the control device is amplified. To this purpose, in all known power steerings the steering action is increased by means of an actuator located between the vehicle frame and the steering device, regardless of the fact that the actuator is of the electrical or hydraulic type or other types. Electrical power steerings of this type have been patented, among the others, by the companies ADWEST ENGINEERING LTD. (WO 9212037, etc.), ALFRED TEVES GMBH (WO 9214640, WO 9212885, etc.), DR. ING. H.C.F. PORSCHE AG (EP 0447626, etc.), HONDA GIKEN KOGYO KABUSHIKI KAISHA (EP 0590576, etc.), KOSHIO SEIKO CO. (EP 0611691, EP 0350817, EP 0460406, EP 0572961, EP 0566168, EP 0556869, EP 0556870, EP 0554703, EP 0531870, EP 0536590, EP 0535422, EP 0611691, EP 0599260, etc.), LUCAS INDUSTRIES (EP 0403234, etc.), MAN NUTZFAHRZEUGE AG (EP 0580997, etc.), MITSUBISHI DENKI KABUSHIKI KAISHA (EP 0360469, EP 0360470, EP 0351087, EP 0361726, EP 0513941, EP 0567991, etc.), MITSUBISHI JIDOSHA KOGYO KABUSHIKI KAISHA (EP 0440365, etc.), NIPPONDENSO CO. (EP 0460582, etc.), REGIE NATIONAL DES USINE RENAULT S.A. (EP 0478437, etc.), ROBERT BOSCH GMBH (EP 0480159, EP 0501017, EP 0545034, EP 0525574, etc.), SEXTANT AVIONIQUE (EP 0522924, etc.), STEERING DEVELOPMENT LTD. (EP 0165758), TEXAS INSTRUMENTS INCORPORATED (EP 0481568, etc.), THE RAYMOND CO. (EP 0490673, EP 0596167, etc.), TOYOTA JIDOSHA KABUSHIKI KAISHA (EP 0531962, etc.), VALEO ELECTRONIQUE (EP 0461037, etc.), VALEO SYSTEMES D'ESSUYAGE (EP 0491601, etc.), VOLKSWAGEN AG (EP 0591653, etc.), ZF FRIEDRICHSHAFEN AG (WO 9314966, WO 9312965, etc.).
On the contrary, in the system of the present invention the pilot's steering work is reduced not by amplifying the force applied along the rotation but conversely by amplifying the angle of rotation along which the force must be applied. To this purpose, the steering column is not continuous, i.e. the connection between the control device and the steering device is not direct as in any known steering system, be it powered or not. The interposition of the motorized device between the control device and the steering device makes possible the amplification or reduction of the rotation, thus achieving a steering angle different from the angle normally produced by the gearing-down built in the steering system. However, it is possible to apply the present steering system in series with a known power steering, thus combining the advantages of both apparatuses.
GB-A-2275032 discloses a control appliance for a vehicle steering system wherein the steering column is divided into an input shaft and an output shaft with a motorized drive therebetween, in the form of a self-locking electric motor. However, this system is an automatic steering control system aimed at satisfying the highest safety requirements while avoiding as far as possible the irritation of the driver caused by its automatic intervention on the front steered wheels, said intervention being intended to compensate for particular driving conditions (e.g. side wind) detected by relevant sensors. Such a kind of operation implies that the system acts only when the input signals from the sensors indicate that an automatic intervention is required, while trying to minimize the effect of the correction on the steering wheel. This is quite the opposite of the operation of the present system, whose activation can only be determined by the input coming from the driver through the movement of the steering wheel. Therefore, it is clear that such an automatic control system is not designed to help the driver in his steering action but rather to provide an autonomous steeering action possibly superimposed on the driver's one.